Manufacturing and Characterisation of Polymeric Membranes for Water Treatment and Numerical Investigation of Mechanics of Nanocomposite Membranes

Predicting the wicking rate of nitrocellulose membranes from recipe data: a case study using ANN at a membrane manufacturing in South Korea

Lateral flow assays have been widely used for detecting coronavirus disease 2019 (COVID-19). A lateral flow assay consists of a Nitrocellulose (NC) membrane, which must have a specific lateral flow rate for the proteins to react. The wicking rate is conventionally used as a method to assess the lateral flow in membranes. We used multiple regression and artificial neural networks (ANN) to predict the wicking rate of NC membranes based on membrane recipe data. The developed ANN predicted the wicking rate with a mean square error of 0.059, whereas the multiple regression had a square error of 0.503. This research also highlighted the significant impact of the water content on the wicking rate through images obtained from scanning electron microscopy. The findings of this research can cut down the research and development costs of novel NC membranes with a specific wicking rate significantly, as the algorithm can predict the wicking rate based on the membrane recipe.

Potential and Design Parameters of Polyvinylidene Fluoride in Gear Applications

(1) Background: With the ever-increasing number of polymer materials and limited data on polymer gear calculations, designers are often required to perform extensive experimental testing in order to establish reliable operational data for specific gear applications. This research investigates the potential of a Polyvinyldene fluoride (PVDF) polymer material in gear applications, considering various loading conditions and different types of gear transmission configurations, including both self-mated mesh and steel/PVDF mesh. (2) Methods: PVDF gear samples were tested on a specially designed test rig that enables active torque control and temperature monitoring in order to obtain the necessary design parameters and failure modes. Each test for certain load conditions was repeated five times, and to fully investigate the potential of PVDF gear samples, comparative testing was performed for Polyoxymethylene (POM) gear. (3) Results: Tribological compatibility, tooth load capacity, and lifespan assessment, along with the types of failure, which, for some configurations, include several types of failures, such as wear and melting, were determined. Temperature monitoring data were used to estimate the coefficient of friction at the tooth contact of analyzed gear pairs, while optical methods were used to determine a wear coefficient. (4) Conclusions: The tribological compatibility of polymer gear pairs needs to be established in order to design a gear pair for a specific application. PVDF gear samples mated with steel gear showed similar lifespan properties compared to POM samples. Temperature monitoring and optical methods serve as a basis for the determination of the design parameters. PVDF is an appropriate material to use in gear applications, considering its comparable properties with POM. The particular significance of this research is reflected in the establishment of the design parameters of PVDF gear, as well as in the analysis of the potential of the PVDF material in gear applications, which gives exceptional significance to the current knowledge on polymer gears, considering that the PVDF material has not previously been analyzed in gear applications.

Halloysite Nanotube-Enhanced Polyacrylonitrile Ultrafiltration Membranes: Fabrication, Characterization, and Performance Evaluation

This research focuses on the production and characterization of pristine polyacrylonitrile (PAN) as well as halloysite nanotube (HNT)-doped PAN ultrafiltration (UF) membranes via the phase inversion technique. Membranes containing 0.1, 0.5, and 1% wt HNT in 16% wt PAN are fabricated, and their chemical compositions are examined using Fourier transform infrared (FTIR) spectroscopy. Scanning electron microscopy (SEM) is utilized to characterize the membranes' surface and cross-sectional morphologies. Atomic force microscopy (AFM) is employed to assess the roughness of the PAN/HNT membrane. Thermal characterization is conducted using thermal gravimetric analysis (TGA) and differential thermal analysis (DTA), while contact angle and water content measurements reveal the hydrophilic/hydrophobic properties. The pure water flux (PWF) performance of the porous UF water filtration membranes is evaluated at 3 bar, with porosity and mean pore size calculations. The iron (Fe), manganese (Mn), and total organic carbon (TOC) removal efficiencies of PAN/HNT membranes from dam water are examined, and the surfaces of fouled membranes are investigated by using SEM post-treatment. Mechanical characterization encompasses tensile testing, the Mori-Tanaka homogenization approach, and finite element analysis. The findings offer valuable insights into the impact of HNT doping on PAN membrane characteristics and performance, which will inform future membrane development initiatives.

CO2/CH4 separation performance of SiO2/PES composite membrane prepared by gas phase hydrolysis and grafting coating in gas-liquid membrane contactor: A comparative study

The gas-liquid membrane contactor (GLMC) is a new and promising kind of gas separation technique, but still exhibits limitations, especially in membrane performance. In order to solve the above problems, we fabricated and characterized novel OH/SiO2/PES composite membranes using gas phase hydrolysis and graft coating methods, respectively. In the preparation process, whether to use alkali to pretreat the membrane was used as an evaluation index. The CO2/CH4 separation performance was tested using the modified OH/SiO2/PES hollow fiber membrane as the membrane contactor in GLMC. In the experiment, we conducted a single factor experiment with diethanolamine (DEA) as the adsorbent to analyze the effect of the flow rate and concentration of DEA on the separation of CO2/CH4. The collected gas had a CH4 content of 99.92% and a CO2 flux of 10.1059 × 10-3 mol m-2 s-1 while DEA at a concentration of 1 mol/L was flowing at a rate of 16 L/h. The highest separation factor occurred at this moment, which was 833.67. Overall, the CO2/CH4 separation performance in GLMC was enhanced with the use of the fluorinated OH/SiO2/PES composite membrane.

Microplastics in wastewater treatment plants: Sources, properties, removal efficiency, removal mechanisms, and interactions with pollutants

Since wastewater treatment plants (WWTPs) cannot completely remove microplastics (MPs) from wastewater, WWTPs are responsible for the release of millions of MPs into the environment even in 1 day. Therefore, knowing the sources, properties, removal efficiencies and removal mechanisms of MPs in WWTPs is of great importance for the management of MPs. In this paper, firstly the sources of MPs in WWTPs and the quantities and properties (polymer type, shape, size, and color) of MPs in influents, effluents, and sludges of WWTPs are presented. Following this, the MP removal efficiency of different treatment units (primary settling, flotation, biological treatment, secondary settling, filtration-based treatment technologies, and coagulation) in WWTPs is discussed. In the next section, details about MP removal mechanisms in critical treatment units (settling and flotation tanks, bioreactors, sand filters, membrane filters, and coagulation units) in WWTPs are given. In the last section, the mechanisms and factors that are effective in adsorbing organic-inorganic pollutants in wastewater to MPs are presented. Finally, the current situation and research gap in these areas are identified and suggestions are provided for topics that need further research in the future.

Characterisation and modelling the mechanics of cellulose nanofibril added polyethersulfone ultrafiltration membranes

The performance of the membranes can be improved by adding the appropriate amount of nanomaterials to the polymeric membranes that can be used for water/wastewater treatment. In this study, the effects of polyvinylpyrrolidone (PVP), the impact of different amounts (0.5% and 1% wt.) of cellulose nanofibril (CNF), and the combined effects of PVP-CNF on the properties/performance of the polyethersulfone-based (PES-based) membrane are investigated. All PES-based ultrafiltration (UF) membranes are manufactured employing the phase inversion method and characterised via Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and the relevant techniques to determine the properties, including porosity, mean pore size, contact angle, water content, and pure water flux tests. Furthermore, the thermal properties of the prepared membranes are investigated using thermal gravimetric analysis (TGA) and differential thermal analysis (DTA) techniques. Experimental and numerical methods are applied for the mechanical characterisation of prepared membranes. For the experimental process, tensile tests under dry and wet conditions are conducted. The finite element (FE) method and Mori-Tanaka mean-field homogenisation are used as numerical methods to provide more detailed knowledge of membrane mechanics.

Characterisation and Mechanical Modelling of Polyacrylonitrile-Based Nanocomposite Membranes Reinforced with Silica Nanoparticles

In this study, neat polyacrylonitrile (PAN) and fumed silica (FS)-doped PAN membranes (0.1, 0.5 and 1 wt% doped PAN/FS) are prepared using the phase inversion method and are characterised extensively. According to the Fourier Transform Infrared (FTIR) spectroscopy analysis, the addition of FS to the neat PAN membrane and the added amount changed the stresses in the membrane structure. The Scanning Electron Microscope (SEM) results show that the addition of FS increased the porosity of the membrane. The water content of all fabricated membranes varied between 50% and 88.8%, their porosity ranged between 62.1% and 90%, and the average pore size ranged between 20.1 and 21.8 nm. While the neat PAN membrane's pure water flux is 299.8 L/m² h, it increased by 26% with the addition of 0.5 wt% FS. Furthermore, thermal gravimetric analysis (TGA) and differential thermal analysis (DTA) techniques are used to investigate the membranes' thermal properties. Finally, the mechanical characterisation of manufactured membranes is performed experimentally with tensile testing under dry and wet conditions. To be able to provide further explanation to the explored mechanics of the membranes, numerical methods, namely the finite element method and Mori-Tanaka mean-field homogenisation are performed. The mechanical characterisation results show that FS reinforcement increases the membrane rigidity and wet membranes exhibit more compliant behaviour compared to dry membranes.

Garlic peel based mesoporous carbon nanospheres for an effective removal of malachite green dye from aqueous solutions: Detailed isotherms and kinetics

Biowaste based nanoadsorbents have gained much attention in the recent times for wastewater decolourization owing to their low cost, high surface area and high adsorption capacities. In the present research, garlic peel based nanoparticles (GCNP) were synthesized at different temperatures by a one step pyrolytic green approach for the effective removal of cationic dye, malachite green from the aqueous medium. The surface properties of Garlic nanoparticles were elucidated by N₂ adsorption- desorption and all the GCNP samples were found to exhibit Type IV(a) isotherm indicating the presence of mesopores in carbon matrix. Using BET calculations, highest surface area (380 m²/g) was obtained for GCNP synthesized at 1000 ^◦C. Characterization of nanoparticles was done by XRD, EDAX, SEM and FTIR studies before and after the dye treatment. Adsorption studies conducted using different parameters like contact time, concentration and pH and dosage of adsorbent showed removal efficiency above 90% for the contact time of 70 min. Best adsorption experimental results were obtained for GCNP synthesized at 1000 °C ascribable to its high surface area, higher total pore volume (0.26 cm²/g) and higher carbon content. Four adsorption isotherm models were used to validate batch equillibrium studies and the results showed data in good agreement with Langmuir and Freundlich isotherms with maximum Langmuir adsorbtion capactiy to be 373.7 mg/g. Kinetic modelling of the data showed best fit with the Pseudo second order model with rate constant value of 48.726 g mg^-1 min^-1. Regenerative studies were conducted conducted upto 6 cycles. Also the GC nanoparticles were tested for their compatibility in membrane form wherein, removal efficiency results were obtained for GCNP anchored in polyvinyl difluoride (PVDF) and polysulfone (PSF) membrane matrix for dye adsorption.

Fabrication of Electrospun Xylan-g-PMMA/TiO2 Nanofibers and Photocatalytic Degradation of Methylene Blue

Herein, xylan-g-PMMA was synthesized by grafting poly(methyl methacrylate) (PMMA) onto xylan and characterized by FT-IR and HSQC NMR spectroscopies, and the xylan-g-PMMA/TiO₂ solution was used to electrospun nanofibers at the voltage of 15 Kv, which was the first time employing xylan to electrospun nanofibers. Moreover, the electrospinning operating parameters were optimized by assessing the electrospinning process and the morphology of electrospun fibers, as follows: the mixed solvent of DMF and chloroform in a volume ratio of 5:1, an anhydroxylose unit (AXU)/MMA molar ratio lower than 1:2, the flow speed of 0.00565–0.02260 mL/min, and a receiving distance of 10–15 cm. Diameters of the electrospun fibers increased with increasing DMF content in the used solvent mixture, MMA dosage, and receiving distance. TiO₂ nanoparticles were successfully dispersed in electrospun xylan-g-PMMA nanofibers and characterized by scanning electron microscopy, energy dispersive X-ray diffraction spectrum, and X-ray photoelectron spectroscopy, and their application for methylene blue (MB) degradation presented above 80% photocatalytic efficiency, showing the good potential in water treatment.

Nanolatticed Architecture Mitigates Damage in Shark Egg Cases

Structural versatility and multifunctionality of biological materials have resulted in countless bioinspired strategies seeking to emulate the properties of nature. The nanostructured egg case of swell sharks is one of the toughest permeable membranes known and, thus, presents itself as a model system for materials where the conflicting properties, strength and porosity, are desirable. The egg case possesses an intricately ordered structure that is designed to protect delicate embryos from the external environment while enabling respiratory and metabolic exchange, achieving a tactical balance between conflicting properties. Herein, structural analyses revealed an enabling nanolattice architecture that constitutes a Bouligand-like nanoribbon hierarchical assembly. Three distinct hierarchical architectural adaptations enhance egg case survival: Bouligand-like organization for in-plane isotropic reinforcement, noncylindrical nanoribbons maximizing interfacial stress distribution, and highly ordered nanolattices enabling permeability and lattice-governed toughening mechanisms. These discoveries provide fundamental insights for the improvement of multifunctional membranes, fiber-reinforced soft composites, and mechanical metamaterials.

Effects of Fe(OH)3 and MnO2 Flocs on Iron/Manganese Removal and Fouling in Aerated Submerged Membrane Systems

Many treatment methods are used to remove iron and manganese from water. Aeration and membrane filtration are two of these methods. In this study, Fe²⁺ and Mn²⁺ removal by aeration with different catalysts and instead of simple membrane filtration applied in other studies, the aerated-submerged membrane systems were evaluated separately. When Fe(OH)₃ was applied in the aeration step and complete oxidation of Fe²⁺ was obtained after 27 min, while complete Mn²⁺ oxidation was obtained in 76 min. However, when MnO₂ was applied in the aeration step, complete oxidation of Fe²⁺ and Mn²⁺ was relatively slow (36 and 110 min, respectively). According to the results obtained from the aerated membrane system, Fe²⁺ and Mn²⁺ removal were extended by Fe(OH)₃ via adsorption/surface oxidation. It is clearly shown from the flux, resistance results, scanning electron microscope (SEM) and Fourier transform infrared (FT/IR) spectroscopy observation that manganese oxides were deposited mainly in membrane pores forming membrane fouling by small flocs, while iron oxide particles were deposited on the membrane surface. Although the flux performance of PT PES membrane was higher than HF PP membrane, fouling resistance of HF PP membrane was higher than PT PES.